This invention relates to a circuit providing coupling around an electric power utility distribution transformer in both directions for a power line communications signal.
Electric power utility distribution transformers exhibit a wide variety of configurations, such as, for example, phase-to-phase connected single phase transformer, delta/delta, open-delta/open-delta, delta/floating-wye and floating-wye/delta. Some of the distribution transformer configurations are either inefficient or totally ineffective in passing a power line communications signal from the primary to the secondary or vice versa. The present invention describes a circuit for effectively coupling a communications signal in both directions around a distribution transformer. The circuit of the invention has a number of advantages, including its ability to be used with a very wide variety of distribution transformer configurations.
One of the principal advantages of the present invention relates to the fact that prior art circuits generally include a capacitor which must have a voltage rating at the level of the primary voltage of the distribution transformer. By contrast, the present invention teaches the use of a relatively small capacitor rated at the secondary voltage of the distribution transformer.
An additional advantage of the present invention is that means are afforded to provide a signal voltage transformation ratio approximately equal to the power voltage ratio of the bypassed transformer. Thus the signal level at the secondary is in the same level range as if it had passed through the bypassed transformer.